The present invention relates to apparatus for handling containers by the increased handling efficiency of a crane.
Known container cranes are provided with a hanger which hitches the container so as to move in horizontal and vertical directions.
For instance, when the container crane handles the container from a container transport ship to a quay, the containers on the container transport ship are hitched by the hanger, the hanger is moved in vertical and horizontal directions, and the container is deposited on a desired position of the quay. After the container is deposited on the desired position, the hanger is released from the container and is returned toward the container transport ship.
In such container handling operation, as is often experienced, the container crane can not handle the container during the time the crane with its hanger returns to the container transport ship.
If the return path of the hanger is long then the number of the containers handled during a given period may become small and the handling efficiency of the containers decreases. Therefore, there is a demand to solve the above difficulty.
In order to solve the difficulty one problem encountered in handling containers by means of a container crane is how to handle as many containers as possible in a short period of time. One solution that comes to mind is to increase the number of times the hanger hitches containers per unit time by shortening the path of movement of the hanger of the container crane in the air. Methods known in the art for handling containers on the basis of the concept mentioned hereinabove will presently be described.
One of such methods consists in depositing a container hung from the hanger on a container receiving truck provided to the container crane for horizontal movement and moving the hanger to hitch another container. The container thus deposited on the container receiving truck is further deposited in a desired location on the ground by the horizontal movement of the container receiving truck and by means of a yard crane provided independently of the container crane. In this method, the path of movement of the hanger of the container crane is shortened by eliminating from such path a portion thereof between the container receiving position of the container receiving truck and the desired unloading position on the ground, thereby increasing the operation efficiency of the container crane and its yield.
Another method known in the art envisages the provision of a space for temporarily depositing a container on the container crane itself so that the hanger of the container crane can be returned to its place of origin for handling another container after depositing the container in such space. The container deposited in such space is further deposited in a desired location on the ground by means of an auxiliary container handling device supported on the container crane. In this method, shortening of the path of movement of the hanger of the container crane is achieved by eliminating from the path of movement of the hanger a portion thereof between the space for temporarily depositing a container on the container crane and the desired unloading position on the ground, thereby increasing the operation efficiency of the container crane and its yield.
A third method known in the art calls for using another travelling frame independently of the container crane and disposed rearwardly thereof, so as to provide the space for temporarily depositing a container and support the auxiliary container handling device described by referring to the second method. This method makes it possible to achieve shortening of the path of movement of the hanger of the container crane in the same manner as the second method.
In the first method of the prior art, the load applied to wheels of the container crane would increase because the container crane supports the container receiving truck. Thus incorporation of the first method in a container crane already constructed makes it necessary to remodel the container crane on a large scale. Moreover, since the container crane and the yard crane are independent of each other, it is necessary to bring them into suitable relative positions for handling containers in cooperation with each other. This might mean a delay in the time for starting a container handling operation. An added trouble is that the yard crane should be moved to position same in a suitable location when the container crane travels to a location where further container handling operation is going to be performed.
Since the container crane provides thereon the space for temporarily depositing a container and supports thereon the auxiliary container handling device when the second method of the prior art is adopted, the container crane would become too heavy and wheels of the container crane would have to support a heavy load. Thus it is extremely difficult to remodel an existing container crane along the lines suggested by this method.
Adoption of the third method of the prior art, although no increase in the load applied to wheels of the container crane is involved, would make it necessary to bring the container crane and another crane into suitable relative positions for handling containers, in the same manner as described by referring to the first method of the prior art. Thus this method would have the disadvantages that the time for initiating a container handling operation is delayed and that positioning of the container crane relative to another crane should be effected each time the container crane is moved to change places for handling containers during the course of its operation.
It will become apparent that other problems encountered in carrying into practice the aforementioned three methods of the prior art can be solved by the present invention, when the description of a preferred embodiment thereof is considered.